|MOSTAFA, IBRAHIM - South Dakota State University|
|HONG, CHANG OH - South Dakota State University|
|SINGH, SHIKHA - South Dakota State University|
|KUMAR, SANDEEP - South Dakota State University|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2016
Publication Date: 1/25/2017
Citation: Mostafa, I., Hong, C., Singh, S., Kumar, S., Osborne, S.L. 2017. Swithchgrass biomass quality as affected by nitrogen rate, harvest time and storage. Agronomy Journal. 109:86-96.
Interpretive Summary: Switchgrass is being considered as a potential feedstock for cellulosic ethanol production. But many questions have be asked about the impact of biomass storage on feedstock quality. To address this concern a study was imposed on an existing experiment established to evaluate the impact of nitrogen fertilizer rates on switchgrass yield. Treatments evaluated were baling and collecting sub samples over the course of the winter, or delaying harvest (leaving standing switchgrass in the field) and sampling over the course of the winter. Storage of switchgrass in bales for seven months increased cellulose concentration a desirable quality. Additionally storage increased the concentrations of lignin, mineral elements, and N, which has a negative impact on biomass quality for ethanol production. Delaying harvest time from fall to spring, however, increased switchgrass biomass feedstock quality through increasing the concentrations of cellulose and reducing the concentrations of mineral elements and N. Generally, the concentrations of all of the fiber constituents, mineral elements and N were smaller in the delayed harvest biomass compared with those stored in bales. The results from this study conclude that delaying in harvesting of switchgrass can reduce the feedstock quality.
Technical Abstract: The main purpose of this study was to assess the sustainability of switchgrass biomass quality as affected by storage after harvesting, delaying the harvest time, and applying different rates of nitrogen (N). The present study was conducted at Bristol, South Dakota under switchgrass land previously seeded to marginally yielding soybean. The treatments included three rates of N (0, 56, and 112 kg N ha-1) applied yearly to the switchgrass. Each N treatment was replicated four times. All of the plots were harvested in October 2010 and November 2011, and data from two growing seasons (2010 and 2011) were used in this study. An area of 30 m2 of each plot was left without harvesting to represent the delaying of harvest. Fiber constituents (e.g., hemicellulose, cellulose, and lignin), mineral elements, N, and C were determined. Results of the this study revealed that the storage of the fall harvested switchgrass biomass significantly increased the concentrations of hemicellulose, lignin, mineral elements, and N, and slightly increased cellulose concentration leading to a reduction of biomass quality as a source of bioenergy. For example, in 2010 and under the N rate of 56 kg N ha-1, hemicellulose concentration increased by 8%, cellulose by 5%, Ca by 10%, K by 7%, Mg by 11%, and P by 8% from November 2010 to May 2011. Delaying harvest during the two seasons, however, improved the quality of switchgrass biomass through decreasing the concentrations of lignin, N, and mineral elements, and increasing the concentration of cellulose and hemicellulose. For example, the concentrations of mineral elements decreased from December 2011 to May 2012 by 14, 38, 10, 98, 46, 25, 70, 21, and 48%.